Pandas: conditional rolling count

I think there is a nice way to combine the solution of @chrisb and @CodeShaman (As it was pointed out CodeShamans solution counts total and not consecutive values).

  df['count'] = df.groupby((df['col'] != df['col'].shift(1)).cumsum()).cumcount()+1

  col  count
0   B      1
1   B      2
2   A      1
3   A      2
4   A      3
5   B      1